PROJECT SUMMARY Electronic cigarettes, also known as electronic nicotine delivery systems (ENDS), are rapidly spreading around the world, including to low- and middle-income countries (LMICs). This study will help understand the impacts of ENDS and the policies to regulate them. We will collaborate with the International Tobacco Control Policy Evaluation Project, which recently received a large grant to evaluate the impact of ENDS use and its regulations across high-income countries (i.e., Canada, England, US) with contrasting policies. The proposed project would collect original data in Mexico and Guatemala in order to integrate them into this effort. The project has the following specific aims: AIM 1. Compare the initiation and consequences of ENDS use among adolescents in Guatemala and Mexico, two neighboring countries with contrasting tobacco policy environments. We will survey and follow 2000 Guatemalan adolescents to understand what promotes ENDS use and whether it leads them to start using conventional cigarettes. An experiment will assess options for ENDS policy (e.g., warnings, marketing bans). Results will be compared to Mexican youth, from whom we are currently collecting data. AIM 2. Determine the predictors and outcomes for ENDS use among established adult smokers in Mexico. We will survey adult smokers who participated in our prior research, as well as smokers recruited online, in order to understand whether ENDS use reduces harm by helping them quit or reduce the number of cigarettes they smoke. Results will be compared with other countries. AIM 3. Characterize the labeling, design and constituents of ENDS products in Guatemala and Mexico. We will analyze ENDS devices and ?e-liquids? (i.e., liquids that devices vaporize) in both countries, to assess: 1. labeling (e.g., warnings, marketing); 2. device design (e.g., battery strength); 3. e-liquid constituents (e.g., nicotine, flavorings, toxicants). We will assess time trends and cross-country differences. AIM 4. Adapt a simulation model for predicting trends in ENDS and cigarette use, including the public health impact of different ENDS policies. We will build on our prior simulation research in Mexico, using data from Aims 1-3 and ongoing studies to integrate ENDS use into the simulation model. The model will project future trends in nicotine product use and the public health impacts of different policies. By achieving these aims, we will strengthen capacity in Guatemala and Mexico for conducting observational, experimental, and simulation research on ENDS, in order to inform the development of best practices for ENDS policies. The project will build upon research team members' longstanding and fundamental role in tobacco research capacity building across Latin America, so that sound public health policies can be developed to address ENDS and other emerging challenges to tobacco control in the region. 1